Numerical analysis using computer simulation is increasingly carried out in a variety of fields. For example, in the medical field, numerical analysis is carried out to reproduce a coronary circulation, which is a vascular network for delivering oxygen and so on to the heart. In such numerical analysis, the vascular network of the heart is represented by a three-dimensional coronary circulation model. For example, in the coronary circulation model, the vascular network is reproduced by connecting elements having radius information.
Further, for example, there is a technique of generating a three-dimensional model representing at least part of a patient's heart on the basis of the patient-specific data on the geometric shape of the heart. With this technique, a physics-based model relating to the characteristics of patient's blood flow is generated, and the fractional flow reserve within the patient's heart is measured on the basis of the above-mentioned three-dimensional model and the physics-based model.
Please see, for example, Japanese National Publication of International Patent Application No. 2013-534154.
A coronary circulation model may be displayed on a monitor for simulation. For example, a coronary circulation model of a patient's heart is displayed so as to confirm the state of the patient's heart.
However, in the case where the conventional techniques are used to display a coronary circulation model, joints between elements of blood vessel may look unnatural. That is to say, in the data of a coronary circulation model, data on each element of the blood vessels has information about length and radius, and therefore blood vessel elements are in cylindrical shape if they are displayed based on the data. Since the blood vessel elements are cylindrical, a blood vessel at a portion where the blood vessel branches into two looks unnatural because there is generated a gap at a connection portion connecting the thick main blood vessel and the two thin branch blood vessels. If the blood vessels in the displayed coronary circulation model look unnatural, it is difficult to visually identify an abnormal portion in the blood vessels, which is a problem.
In this connection, if a model of the vascular network of any other organ than the heart is approximately displayed with a combination of cylindrical elements, the model looks unnatural, like the coronary circulation model. This problem is not limited to the case of displaying a model representing a vascular network. That is to say, if a model is generated by approximating tubes, which are connected smoothly in nature, with a plurality of cylindrical elements having different radiuses and then is displayed, the model looks unnatural, which is a problem as in the case of displaying a coronary circulation model.